Thunderstorms have moved east of the dvn cwa except in Bureau and Putnam counties so we have cancelled the Flash Flood Watch. As soon as the storms moved out of the cwa entirely the remainder of the watch will be cancelled.

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Synopsis... issued at 245 am CDT sun Sep 15 2019

As of 2 am, two distinct areas of convection were noted on GOES infrared imagery, one across NE Iowa into SW Wisconsin and the other over east- central Iowa into northwest Illinois. The trend over the past few hours has been increasing storm coverage and intensity per cooling infrared cloud tops. Mrms radar estimates 1-2.5 inches of rain has fallen in the past 12 hrs from NE Iowa County through central Johnson, and into central and southern Cedar co. Another hard hit area was central Clinton co. Into portions of Whiteside co. (About 1-2"). Luckily we haven't had to deal with too much training of storms as they have shifted slightly to the south of this hard hit zone.

Late tonight into early this morning

Latest rap analysis indicated a favorable setup for numerous elevated showers and thunderstorms on the eastern periphery of impressive 925-850mb WV transport and a low-level jet. Efficient rain producing storms, with rates up to 1-2 inches per hour, can be expected due to deep warm cloud depths (2-2.5 km warmer than 0 c) and pwats up to 1.50-1.70 inches. Additionally, mid-level lapse rates of 7-7.5 c/km and 1000-2000 MUCAPE will provide ample instability for robust updrafts. Storm motion vectors and mean 850-300mb flow are showing storm speeds of 20-30 mph from west to east. Although, corfidi vectors suggest some potential for backbuilding meso-Beta elements and threat for localized heavy rain totals of 2-3+ inches.

Hi-res models have come into better agreement on the most likely location for the highest quantitative precipitation forecast to be over the central to east- central sections of the cwa, probably staying to the south of the Freeport area.

The Flash Flood Watch remains in effect in the north and northeast where recent heavy rainfall has led to saturated ground and has lowered 1 hr flash flood guidance to 1-1.5 inches. Since the heaviest rain axis has shifted a little to the south, the watch was expanded to include the counties along I-80 from the Quad Cities and points to the east.

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Short term...(today and tonight) issued at 245 am CDT sun Sep 15 2019

Today

Scattered showers and storms will linger in the east and southeast through the mid morning before completely diminishing and moving east of the forecast area. The rest of today will be very warm and humid with highs in the low 80s north to upper 80s south, and dewpoints into the upper 60s to low 70s. There could be an isolated shower or storm that develops in the east this afternoon near peak heating but chances are very low.

Little change to the extended forecast with hot (for mid september) and humid conditions likely through the week ahead. An expansive upper ridge will be in control over the central U.S. Forecast highs are in the 80s and dewpoints into the low 70s at times, which will yield peak heat indices in the upper 80s to lower 90s making it feel more like mid Summer than mid September.

A shortwave trough, tracking through the northern plains into southern Canada, will flatten the northern edge of the upper ridge mid to late week. A weak front associated with this system is our next chance for showers and thunderstorms. Have low chances in the forecast from Wednesday evening (in the west) through Friday, which is reasonable due to expected low areal coverage and limited influence from the shortwave due to its northern track.

Models are in better agreement on the front either washing out or not making it completely through the central or southern forecast area before retreating north again on Thursday and Friday. Main message is the unseasonably warm and humid conditions look to be locked in through at least next Saturday. Uttech

Scattered thunderstorms with heavy rain will impact kbrl over the next 1-2 hours with periods of MVFR/IFR visibilities. A deck of stratus clouds has been expanding over northeast Iowa, which will likely lead to MVFR ceilings at kdbq this morning, kcid will be on the southern edge. Areas of fog are expected tonight and it could become locally dense. Confidence is low on exactly where the dense fog develops at this lead time; have MVFR visibilities in the tafs for now.

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Hydrology... issued at 1129 am CDT Sat Sep 14 2019

Routed water moving through the river systems along with additional heavy rain potential tonight is causing forecast rises, many within bank rises, across the area.

The hardest hit local basins have been the Pecatonica and Rock River basins and we are getting a better handle on the flows from rains that already fell, however there does remain a bit of uncertainty on how high the crests will be. The Pecatonica in Freeport is cresting currently and will fall less than a foot before starting to go up again as more water moves down from upstream.

On the rock, the forecast for the gage at como has gone down this morning and the rate of rise has slowed, giving less confidence that the river will hit the flood stage of 12.5 ft even though it's only a half foot from that level currently. Because of this, opted to hold onto the Flood Watch and will re-evaluate this afternoon. Downstream at Joslin, it may be noticed that the hydrograph is now showing the river to rise to 14.1 feet. Think the rise is going to be very near 14 ft, but don't have enough confidence that it will reach or exceed 14 ft to put out a new Flood Warning for moderate flooding yet. Will continue to monitor.

There is a chance for heavy rains tonight, if heavier rains fall than is expected, additional river flooding could occur.